In a variety of packaging equipment, it is important to be able to feed individual sheets or portions thereof continuously and uninterruptedly into an assembly machine, and one illustration of this is to provide a continuous stream of plastic sheets into a beverage container packing operation, so as to provide a carrier or cover mechanism for a plurality of the container. Such a package is illustrated in the Bonkowski U.S. Pat. Nos. 4,688,367 and 4,281,502.
The preferred plastic sheet of the present invention is a web approximately 10 mil thick of recycled polyethylene terephthlate approximately 8-12" wide. A suitable material is DuPont's polyethylene film PTX-266 (DuPont Trademark SEALER PT).
In order for this material to be continuously and effectively provided at high speed into the container packaging machinery, individual sheets must be fed at spaced intervals, and it has been found inconvenient and impractical to do this from a stack of pre-cut sheets because the characteristics of the material cause such sheets to "block" in the stack and make it relatively impossible to feed them accurately into the machine.
Thus it is an object of the present invention to provide a web of the material in roll form, which can be more readily perforated to provide continuous inter-connected sheets readily unwound from the larger roll.
The apparatus of the present invention includes two supports, or unwind stands each one holding a roll of the web material. One of the webs is fed into a staging roller, which carries a plurality of radially outwardly extending pins which engage in the holes punched in the web of material. Surrounding the staging roller is a capture device, which keeps the sheet in close contact with the roller.
A second stand with a second roll of web material is fed onto a second staging roller, also supplied with a capturing device, and on this second staging roller the second web of material waits in readiness for it to be inserted, on command, into the feeding mechanism, when the web from the first roll has been depleted.
Because the material involved in the present invention is sufficiently stiff so that it can be pushed (rather than being pulled), the first staging roller pushes the first web of material into contact with a moving belt which, itself, has a plurality of pins extending outwardly therefrom. The spacing and the timing of the staging roller and the continuous belt are such that the web is carried directly from the staging roller onto the continuous belt by the pins which are moving at the same linear speed.
A preferred speed for the packaging of six or twelve packs of beverages is from 50 to 200 ft./minute.
Adjacent the continuous belt is a fracturing station, which carries a perforation breaker. The action of the perforation breaker and the movement of the continuous belt is such that the perforation breaker presses against the web when a line of perforations is directly opposite the perforation breaker. This separates the preceding web material from the following web material.
In a preferred embodiment, the line of perforations are separated on the web by 10.5", which is appropriate for the length of a sheet of plastic to cover the commercially accepted 12-pack of beverage containers.
After the web has been separated at the line of perforations by the perforation breaker, one of the sheets is carried by the belt around an accelerator roll, which speeds up the movement of the plastic sheet to bring it into linear speed-conformity with the assembly of containers against which the sheet is to be placed.
The assembly of containers is moving along at a 12" pitch, and thus the sheet is speeded up as it turns past the accelerator roll from 10.5" pitch to 12" pitch, and thus the sheet and assembly of containers can be carried in to the packaging machine as desired.
When the first roll of web material is depleted, a detector such as a dancing roller which may be a type of limit-switch assembly detects the end of the web, and signals the "tail breaker" to make one revolution to separate the remaining "tail" of the web.
The second staging roller receives the same signal as the first staging roller, and they rotate in unison so that the leading edge of the second web on the second staging roller is pushed into contact with the continuous belt, so that the leading edge of the second web is immediately behind and in contact with the trailing edge of the first web, and thus there is no discontinuity in the feeding of sheets into the package assembly area.
Thus it is a principal object of the present invention to provide a feeder for individual sheets of plastic material into a packaging machine without any discontinuity in the feeding operation.
A further object of the invention is to provide a sheet separator and accelerator which receives a perforated and punched web of material and separates from it individual sheets.
With the above and other objects in view, more information and a better understanding of the present invention may be achieved by reference to the following detailed description.